"In the course of 2009, risky assets will outperform safe assets," says Doll. "If you're hiding in Treasury bills and notes, it's time to put some of it to work."

Doll adds the hardest time to invest is generally the best time.

"I'm not saying we're going straight up from here, don't get me wrong," he adds. "But I do believe it is a time to say, 'Okay, markets have gone down a lot, now where are we? Forget about what has happened. What might happen from here?'"

Investors who feel compelled to wait until the market appears more solid could end up costing themselves money in the long run.